Characteristics of toxic metal accumulation in farmland in relation to long-term chicken manure application: a case study in the Yangtze River Delta Region, China.

Characteristics of toxic metal accumulation in farmland in relation to intensive chicken manure application on a regional scale was studied in this paper. Concentrations of Zn, As and Cu in manure exceeded the related standard in 66.7%, 14.3% and 16.7% of samples, respectively. Among chicken feed samples, concentrations of Zn, Cr and As exceeded the National Standard limits in 74.3%, 56.3% and 34.3% of samples, respectively. The accumulation of metals in soils from long-term chicken manure application has led to increasing uptake in above-ground shoots of wheat. The maximum contents of all metals present in the soil are currently below the threshold values of National Grade II criteria. At present, the farmland soil is safe for agricultural production, but more attention should be given to the potential environmental risk of metal accumulation in chicken manure and soils.